Plastics and other polymers are in theory recyclable, but after a relatively short functional life, are destined to arrive as a significant component of trash. Most of these plastics and other polymers disposed of in landfills are chemically stable and degrade minimally.
This is an increasing problem of plastic pollution in the environment, while the demand for plastics keeps on increasing in most consumer products. Furthermore, the availability of landfill space is diminishing, while there is a worldwide trend toward more stringent regulatory requirements on landfills. Some research and commercial efforts have been directed toward the development of new uses for polymerized products such as scrap, waste tires or rubber. However, because of the high costs associated with the use of plastics this approach has not gained wide acceptance. It is therefore necessary to develop alternative pathways for production of a new class of plastics and a considerable amount of attention has been devoted towards recycling and reclaiming plastics and other polymers.
There are two broad groups of polymers and copolymers classified according to their polymerization: a) condensation polymers, for example polyesters, nylon or polycarbonates, and polyurethane having a polymerized form with a lower molecular weight than the sum of monomers used to make them, and b) chain growth or addition polymers, such as polyethylene and polypropylene have the same molecular weight as the sum of the monomers used to make them, and are made in specific conditions of temperature and pressure and in the presence of a catalyst. Importantly, the instant degradation processes of the present invention can be applied to thermoplastic as well as thermoset polymers such as: polyurethanes, unsaturated polyesters, or epoxy resins, by incorporating the latent sulfide bonds into thermoplastic and thermoset resins. Thermoset as defined herein, is a three dimensional bonded resin molecule which is insoluble under routine degradation conditions. It is possible to solubilize the resins in defined aqueous conditions described herein for degrading and recycling the polymers.
Polymers are generally broken down by two ways: pyrolysis and depolymerization. Pyrolysis requires high temperature conditions known as thermal cracking, a process in which polymer molecules are heated until they fragment into several smaller and randomized-sized molecules, for example, a mixture of alcohols or hydrocarbons, none of which is an original monomer.
Depolymerization is carried out at significantly milder thermal conditions than those employed in pyrolysis and prior art teaches several hydrolytic methods, for example, glycolysis, methanolysis or hydrolysis, based on the depolarization reagent used, such as glycol, methanol, or water respectively, wherein under specific conditions of usually high temperature and pressure, with or without a catalyst, the polymer chain separates into its original monomers.
A number of compounds with carbon-carbon double bonds are used in the preparation of polymers. Alkenes of the type CH2═CH—X are used to form polymers of the type as shown below in Table A.
A. Alkenes of the type CH2═CH—X used to form polymers of the typeCompoundStructure—X in polymerApplicationEthyleneCH2═CH2—HPolyethylene films as packaging material;“plastic” squeeze bottles are molded fromhigh-density polyethylene.PropeneCH2═CH—CH3—CH3Polypropylene fibers for use in carpetsand automobile tires; consumer items(luggage, appliances, etc.); packagingmaterial.StyrenePolystyrene packaging, housewares, luggage, radio and television cabinets.Vinyl chlorideCH2═CH—Cl—ClPoly(vinyl chloride) (PVC) has replacedleather in many of its applications; PVCtubes and pipes are often used in placeof copper.AcrylonitrileCH2═CH—C≡N—C≡NWool substitute in sweaters, blankets, etc.Alkenes of the type CH2═Cx2 are used to form polymers of the type (—CH2—CX2—)n as shown below in Table B.B. Alkenes of the type CH2═CX2 used to form polymers of the type (—CH2—CX2—)nCompoundStructureX in polymerApplication1,1-DichloroetheneCH2═CCl2ClSaran used as air- and water-tightvinylidene chloride)packaging film2-MethylpropeneCH2═C(CH3)3CH3Polyisobutene is component of “butyl rubber”,one of earliest synthetic rubber substitutes.Other chemical structures may also be used to form polymers as shown below in Table C.
C. OthersCompoundStructurePolymerApplicationTetrafluoroetheneCF3═CF3(—CF2—CF2—)n(Teflon)Nonstick coating for cooking utensils;bearings, gaskets, and fittings.Methyl methacrylateWhen cast in sheets, is transparent; used as glass substitutes (Lucite, Plexiglass).2-Methyl-1,3-butadieneSynthetic rubber.Source R. C. Atkins and F. A. Carey, Organic Chemistry: A Brief Course, McGraw-Hill, New York, 1990, p. 132. 
Generally fifty percent or over, of the manufactured polymers are used as packaging materials and about ninety percent of this flow finishes as a component of ecological garbage. Much effort has been put into developing synthetic polymers intended for packaging, which are capable of being broken down chemically and physically by environmental actions or by biological processes. Such polymers are described as biodegradable.
Biodegradability can be defined as the degradation at the molecular level of substances by the action of enzymes derived from the metabolic processes of microorganisms. The synthetic polymers may also be collected in a reservoir containing bioactive bacteria and microbes, which degrade the plastics to environmentally non-toxic degradation products. However, problems exist in the recycling and purification of monomer degradation products because these products may not be reincorporated into plastics in a cost-effective process. Moreover, the degradation process is time consuming and bio-hazardous, and often results in accumulation of heaps of biohazardous garbage.
Some polymers are known to degrade by hydrolysis in the presence of water and thereby decompose to smaller chemical units. Some of these polymers are also biodegradable, such as polylactic acid and polyglycolic. Due to the expense and difficultly in preparing these hydrolytically degradable polymers, their use has been largely confined to high cost medical applications where bioabsorbable materials are required.
The object of the present invention is to provide a cost effective and easy to prepare degradable compositions of plastics and other polymers containing the amino-sulfenyl (=—NH—S—), the oxygen sulfenyl (=—O—S—), the disulfide (=—S—S—) moieties, and ways to develop processes for their production and to enable these compositions to be used as instantly degradable plastics. It is also the object of the present invention to develop processes useful to carry out instant degradation of plastic disulfides so that these compositions may be used as instantly degradable plastics.